With the increased use and popularity of laptop and notebook-sized computers it seems to be a common thread that the fragility of the disk drive in portable systems is a major cause of product failure and customer dissatisfaction. Portable computers are generally handled much like calculators, frequently carried from place to place, bounced about, and prone to be being accidentally dropped. The likelihood of fatal damage to the disk storage device is increased if the drive is made removable from the computer to provide for the portability of the information for data interchange, security, and archiving.
In disk drives, the head and disk assembly ("HDA") include not only the most sensitive components, but also the components which are the most expensive. Cost savings accrue more with cost avoidance from not having to replace broken products or loss of future sales to dissatisfied customers.
A typical rigid or hard disk HDA comprises one or more rotatably mounted disks having an extremely thin magnetic coating deposited on the highly polished disk substrate. Information is generally written and read from the magnetic recording surface by a fragile thin film read/write head. The head is usually delicately suspended at the end of a thin flexure which is in turn attached to a cantilevered beam which is radially positionable above the various concentric data recording tracks of the disks.
During operation of the disk drive, the disks rotate at high speed and the heads fly above the recording surfaces on a thin air foil created by the rotation of the disks. Any imperfections in the outer coating of the disks or contaminants present in the environment are likely to interfere with flight of the heads, reducing the performance of the drive.
Major imperfections in the surface topology of the disk or loose particles will cause the heads to crash into the disk surface, making the device unfit for its intended purpose. Also, since the heads fly at an extremely low altitude any unexpected physical movement of the drive may cause the heads to strike the disks, resulting in damage to either the heads, the surface of the disks, or both.
When the disk drive is turned off, the heads are generally "parked" in a rest state on the disk surface. When the heads are parked, the most sensitive direction is perpendicular to the disk surface. If the acceleration applied to the heads exceeds a certain level, decided by the head load and the mass of the head, the head will leap off the disk surface on which it is parked and then slap down marring the surface, and possibly damaging the head and the head suspension components. In the transverse direction the heads are generally more resistant to shock.
Conventional head and disk assemblies are typically shock mounted into an external support frame. However, disk drives having a small form factor, 21/2" and below, do not have such an external frame. Any shock absorbing features are left to the integrator of the drive into the computer system, or to the inherent shock resistance of the components. Commonly, manufacturers of conventional small form factor drives may claim 100 g resistance to shocks, without referencing either the duration or the direction of the shock with respect to the axis of the disk. However, should a drive or the equipment in which it is mounted be dropped from a height of about three feet the de-accelerating force can approach 1000 g.
Therefore, in order to improve the durability of small form factor drives, it is desirable to provide a shock mount frame which decreases their mechanical vulnerability of the HDA components. In addition, the durability of the drive can be improved by hermetically sealing the drive enclosure.